In many countries air-cushion transport vehicles find various applications in different fields of use.
Factors which restrain further application of such vehicles are the following: large overall sizes and weight a device for controlling the reactive thrust and also the complicated construction of mechanisms for effecting the turning of flaps and blades, used in these devices. The overall size and mass weight of the reversing-and-steering devices are mainly determined by the flow capacity of passages which direct the air flow during production of a forward and reverse thrust. Changing the direction of a reactive air stream is accomplished by a system of rotatable and guide blades installed in the exit sections of nozzles or passages.
Known in the art are lift and propulsion units for air-cushion craft, comprising reversing-and-steering devices (cf., for example, a magazine "Air-Cushion Vehicles", Vol. 7, No. 45, March 1966, pp. 33 through 39).
The known lift and propulsion units comprise a centrifugal fan installed in a spiral casing. The spiral casing is provided with a passage delivering air to a reactive thrust nozzle having rotatable rudder blades installed at the exit thereof. For reversing, use is made of a scoop-like flap which closes the passage delivering air to the reactive thrust nozzle and directs the air during reversal toward the craft bow.
Such a reversing device has a substantial mass, requires a special mechanism for turning the flap and generally fails to ensure directional control of the reversed reactive thrust.
Known in the prior art is a lift and propulsion unit for an air-cushion transport vehicle comprising an axial fan disposed in an annular duct (cf., for example, British Pat. No. 1,306,687, Cl.60 V 1/00, issued on Feb. 14, 1973). This unit also comprises a reversing-and-steering device consisting of articulated rotatable louver blades which in combination with flaps close the exit of the air from the annular duct, to provide the reversal of the air stream. The louvers and flaps are controlled from the cabin of a transport vehicle.
Such a reversing device should have a substantial axial size to allow accommodation, in side walls of the annular duct, of individually rotatable louver blades and to permit arrangement, at the exit of the annular duct, of rotatable flaps serving to close the thrust passage with the purpose of obtaining the reversal of the air stream. The device also requires a special mechanism for individually turning the louver blades and the flaps.
On the whole, such a unit is of a substantial axial size and has an additional mechanism for individually turning the louver blades. Therefore, such a unit increases the overall size, complicates the construction and hampers the control of an air-cushion transport vehicle.